Brazilian scientists identify elephant grass as a promising biomass crop; first projects already underway

Studies by the Agrobiology Centre at the state Brazilian Agricultural Research Corporation (Embrapa) are finding that elephant grass has great potential as a biomass crop that can be used for the production of green heat, power and electricity. A Brazilian company, Sykue Bioenergia, has already commissioned a first thermoelectric power plant that will be fuelled by the grass. It plans another 10 and aims for carbon credits. The market for the solid biofuel is potentially huge, as it can further be used in the iron, steel, aluminum, chemical and cement industries. Moreover, the highly efficient crop can be grown across the tropics, opening major perspectives for clean development and new export markets in the developing world. Experts see the emergence of a global solid biofuel market, similar to that of liquid biofuels.

Biomass champion
Elephant grass (Pennisetum purpureum - earlier post) is a species of grass native to the tropical grasslands of Africa. It is a tall perennial plant, growing to 2-4.5m tall (sometimes up to 7.5 m), with razor-sharp leaves 30-120 cm long and 1-5 cm broad. It is a cane-like species of grass which utilizes the efficient C4 carbon fixation path, resulting in high biomass productivity. When burned in biomass power plants it can generate 25 times as much energy as the amount of fossil fuel used to produce it. In short, the crop has an extremely strong energy balance. (Compare with the energy balance of corn ethanol, which is around 1 to 1, or sugarcane ethanol at 8 to 1).

The biomass crop can be used as an alternative to coal, which is fetching record prices (earlier post). As a solid biofuel it can be burned either in dedicated, highly efficient biomass power plants, in blast furnaces as an alternative to coal, or co-fired with coal in existing power plants.

According to Vicente Mazzarella, who has been studying elephant grass at the Sao Paulo state government’s Institute for Technological Research (IPT) since 1991, the crop is a champion when it comes to sheer biomass yields. Compare it with the popular eucalyptus tree, planted in Brazil to produce cellulose and charcoal: the tree yields around 7.5 tons of dry biomass per hectare a year and up to 20 tons a year in optimum conditions, while elephant grass yields 30 to 40 tons.

Furthermore, eucalyptus trees take seven years to reach a size worth felling, while elephant grass can be harvested two to four times a year, because of its rapid growth.

And its yield may be increased still further, since the species has hardly been studied and no genetic improvement efforts have yet been carried out. There are close to 200 varieties of elephant grass, and it will take time and effort to identify which ones are best suited to different soil and climate conditions.

Crop research
After 10 years of research, Embrapa’s Agrobiology Centre identified three varieties of elephant grass suited to energy production purposes because of their high yield without nitrogenous fertilisers. For use as a biofuel, the least nutritious varieties are sought, in contrast to its traditional use as animal feed:
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The reason is that nutrients like mineral salts produce ash that can damage iron and steel furnaces, Bruno Alves, an agronomist with the elephant grass research team at Embrapa’s Agrobiology Centre, headed by Segundo Urquiaga.

That is why tests were done using varieties that grow in poor soil, using the minimum amount of fertilisers, but still producing the highest yields of biomass.

The conversion of energy intake into energy storage (the energy balance) of the plant can be improved by biological nitrogen fixation, in which bacteria take nitrogen from the air and convert it to compounds that fertilise plants.

This is an area in which Embrapa’s Agrobiology Centre has accumulated much expertise in the last few decades, inoculating nitrogen-fixing bacteria into beans and sugarcane.

Biological nitrogen fixation limits itself to the nitrogen required by the plant, avoiding the risk of excessive nitrogenous fertiliser use, said Alves. He pointed out that nitrogenous fertilisers require the greatest amount of fossil fuel energy to produce them chemically, and that by avoiding its use, greenhouse gas emissions are also avoided.

Logistics, bioconversion
But elephant grass does present certain difficulties. It likes a lot of water, so its tolerance of the long dry seasons of the Cerrado, the Brazilian savannah where the largest extensions of land are available for cultivation, must be studied, as well as whether it will maintain its productivity level with less humidity.

Drying and compacting the biomass are also a challenge. Green elephant grass is 80 percent water, and it does not dry out in the sun, as eucalyptus does, but rots if left in piles. To dry, it must be cut up into small pieces, and some heat energy applied. Compacting is necessary for storage and transport because of the great bulk of the dry grass.

The ceramic industry, therefore, is likely to be the first user of elephant grass as an energy source. Medium-sized ceramic plants require less than 100 hectares of elephant grass grown nearby, which dispenses with compacting and transport. The dried elephant grass can be used in furnaces directly, instead of wood or natural gas. Other processes needing just heat or steam will soon be able to make use of this alternative fuel.

First grass powered station
A medium-sized electricity company, Sykue Bioenergia, has already commissioned a thermoelectric power plant that will be fuelled by elephant grass. The thermoelectric station will be built in Sao Desiderio in the state of Bahia in northeastern Brazil, by Dedini, an industrial company better known for building sugar mills and distilleries.

The Sykue power plant will cost 80 million reais (43 million dollars) and is due to come onstream in December 2008. It will have a capacity of 30 megawatts and will produce its own elephant grass on a plantation of 4,000 hectares. The company intends to build 10 such power plants soon.

Ana Maria Diniz of Sykue Bioenergia said grass had been chosen to power the new generating plant “due to its capacity to transform solar energy into cellulose via a totally clean, renewable and economically viable production cycle.”

The project will allow carbon credits of a million tons per year to be obtained, which can be sold on the international market to generate extra profits for the companies involved.

Huge market
Making charcoal from elephant grass, to substitute for coke or traditional charcoal made from wood, still needs further research. But environmental pressures and the threat of an energy deficit in Brazil may accelerate its development and stimulate investment from large steelworks and energy companies.

The potential demand for this alternative energy source is huge, said Mazzarella, who indicated five big markets. As well as steelworks interested in a new charcoal that does not contribute to deforestation, there is a group of large consumers of energy, such as the aluminium industry, the chemical and cement industries, and electricity distributors.

Biomass energy implies a key saving for electricity companies because it can supply extra electricity at times of peak demand, which is the most expensive to produce.

The mining industry, which imports coal to process iron ore into iron and steel for export, could use elephant grass compressed into pellets, similar to wood pellets, in its blast furnaces as an economical and environmentally friendly solution.

In Europe, the use of dry, compacted biomass pellets for heating is growing rapidly (earlier post, here and here), and elephant grass could open up export markets for Brazil similar to those for ethanol, Mazzarella said.

References:
IPS: Pasto elefante, nuevo campeón en biomasa - October 2007.

Fuel Alternative: Brazil to produce power from grass - July 24, 2007.

Biopact: E.ON UK submits application for 25MW biomass plant - July 20, 2007

Biopact: Biomass pellets revolution in Austria: 46% less costly than heating oil; most efficient way for households to reduce carbon footprint - October 06, 2007

Biopact: Report: biomass fastest growing renewable in EU, largest potential - September 15, 2007

Biopact: Interpellets 2007: conference looks at wood pellets as an alternative to fossil fuels - August 16, 2007